Mercury thermometers are about to be discontinued. What will be more reliable for measuring body temperature in the future?

Review expert: Wu Xinsheng, deputy chief physician of gastroenterology department

Recently, "H1N1" has become a hot topic again. Many friends have unfortunately been infected, and some classes have even been suspended due to the large number of infected people. At the same time, many drugs, including oseltamivir, are in short supply, and the various drugs stockpiled during the epidemic have once again become good things to relieve symptoms.

During the epidemic, a netizen shared on a short video platform that he spent 2,000 yuan to buy an industrial infrared thermometer, saying that it could not accurately measure body temperature and was not as good as a ten-yuan mercury needle, which was ridiculous.

Source: Shangguan News

In fact, although industrial thermometers have high accuracy, they are used differently from thermometers, and it is actually difficult to obtain accurate results when using them to measure body temperature.

Infrared thermometers for measuring body temperature are also often seen. The most common example is at the entrance of subways and train stations, where there is usually a machine with a display screen. When someone enters the camera range, the body temperature is displayed. In fact, it uses the principle of infrared temperature measurement.

In actual applications, infrared temperature measurement is mostly used in clinical and public places. It is a non-contact temperature measurement that can quickly screen out people with abnormal body temperature. However, in actual temperature measurement, its accuracy is lower than that of mercury and electronic thermometers. The reason is that infrared temperature measurement is greatly affected by the environment .

Why is the infrared thermometer inaccurate? Let me first explain the principle of infrared temperature measurement.

Most substances in nature will continuously emit infrared rays due to molecular motion, and the amount of infrared rays will increase as the temperature rises. Infrared detectors can capture these emitted rays and convert them into infrared thermal images, from which the temperature can be seen.

Source: Guangzhou Daily

This type of testing does not require direct contact and can greatly reduce the risk of infection.

Although infrared temperature measurement is fast and safe, it has a big disadvantage. Infrared thermometers on the market basically have a temperature range for the environment they are used in. They cannot be used in environments that are too cold or too hot. For example, subway stations are relatively closed environments. When there are many people, the environment becomes hot, and infrared temperature measurement is inaccurate.

Source: Guangzhou Daily

Infrared thermometers are included in the national certified measuring instruments catalog and meet the temperature measurement standards, but due to ambient temperature limitations, they are more commonly used for temperature screening of the crowd.

So in daily household use, what kind of thermometer should we choose to accurately measure the temperature?

What types of thermometers are there?

There are four commonly used thermometers: mercury thermometer, electronic thermometer, ear thermometer and forehead thermometer.

1. Mercury thermometer

Mercury thermometers are widely used in homes and hospitals because they are more accurate than electronic and infrared thermometers.

Source: Baidu Encyclopedia

Mercury has a strong thermal conductivity and can accurately measure any temperature change, but mercury needles also have many disadvantages.

First, the mercury needle needs to be shaken every time it is used to reset the mercury; second, the mercury needle is easy to fall and break during use. Mercury is a toxic and volatile metal. If it is not cleaned in time, it can easily cause damage to the human body; third, the mercury needle is not convenient for observation because of its fine scale.

The National Medical Products Administration also issued a related notice in 2020, banning the production of mercury-containing thermometers and mercury-containing sphygmomanometers by 2026. In the near future, the mercury needles that have been with us for decades will be replaced.

2. Electronic thermometer

Electronic thermometers measure temperature through temperature sensors and need to be equipped with batteries to use. They are contact thermometers and need to be placed in the mouth, armpits, anus, etc. according to temperature measurement requirements.

Source: pixabay

The maximum allowable temperature error of an electronic thermometer is between ±0.2℃, which will not delay the diagnosis of the disease. As long as the measurement method is correct and the battery is replaced regularly, it can be used with confidence.

3. Ear thermometer and forehead thermometer

Although ear thermometers and forehead thermometers are used with batteries, they are not "electronic thermometers" but infrared thermometers. The reading is not only affected by the ambient temperature, but also by whether the ear canal is clean and whether the forehead is sweating.

Source: Baidu Encyclopedia

Despite this, many hospitals use ear thermometers to quickly identify abnormal body temperatures, so they can be used with confidence.

In general, mercury thermometers have the highest accuracy, so you need to pay attention to safety when using them at home. In the future, they will be replaced by electronic thermometers. Although there are some errors, they will not affect the diagnosis of the disease.

As for infrared thermometers, they do not require such a long measurement time. They are more for rapid screening and are given to infants or special groups. They are also sufficient as a reference for medical conditions.

Source: pixabay

At present, regular thermometer products must be approved by the state, that is, obtain a CPA certificate, before merchants can produce and sell them. Consumers can judge and choose by the CPA logo and number when purchasing.

How to use the thermometer correctly

If you want to measure your body temperature accurately, on the one hand you need to know how to choose it, and on the other hand you need to know how to use it correctly.

For example, mercury thermometers should be used without bumping, and special attention should be paid when swinging them back to zero. To prevent the mercury in the thermometer from flowing out and causing harm, the red line should be shaken to a point without scale before use; when using an ear thermometer, the ear canal should be kept clear and free of impurities, and the temperature probe should be directly pointed at the eardrum to accurately measure the temperature; when using a forehead thermometer, measure against the forehead, and it is recommended to measure indoors.

No matter which thermometer you use, do not exercise, eat, drink hot or cold water, take a bath, or do other things that may affect your body temperature before measuring. For example, before measuring the oral cavity, try not to eat or drink, and the temperature contact part should be placed under the tongue; when measuring the armpit, hold the thermometer tightly in the armpit and keep the armpit dry.

Source: pixabay

Having said that, do you have a better understanding of thermometers?

In short, no matter what kind of thermometer, it is impossible to be perfect, each has its shortcomings, but in actual use, you don’t need such absolute numbers. If you feel uncomfortable, take a rest and seek medical treatment in time. After all, health is more important than anything else, and being healthy is the most important thing.